1979: Shah and his family are forced into exile. Islamic fundamentalist Ayatollah Ruhollah Khomeini returns to Iran after 14 years of exile in Iraq and France for his opposition to the regime. Islamic Republic of Iran is proclaimed.

1979: In November, a group of Islamic militants takes 52 Americans hostage inside the U.S. Embassy in Tehran. They demand the return of the Shah from the U.S. to face trial in Iran.

1981: American hostages are released after 444 days in captivity. President Ronald Reagan begins first of two terms in office.

1985: Reagan administration officials work covertly to sell arms to Iran in exchange for the release of seven American hostages held by Iranian-backed militants in Lebanon and to pay the Contras fighting the Sandinistas in Nicaragua’s civil war. The events become known as the Iran-Contra affair.

1988: Iran and Iraq reach agreement to end war in U.N.-brokered deal.

1989: Ayatollah Khomeini dies; President Ali Khamenei appointed new supreme leader. Ali Akbar Hashemi-Rafsanjani, speaker of the National Assembly, becomes president. U.S. releases $567 million in frozen Iranian assets.

1990: Iran stays neutral during Iraq's invasion of Kuwait.

1995: U.S. puts oil and trade sanctions on Iran, accusing the country of sponsoring terrorism, violating human rights, seeking nuclear arms and trying to sabotage the Arab-Israeli peace process. Iran rejects the charges.

2002: President George Bush says Iraq, Iran and North Korea are part of an "axis of evil." He warns that Iran and the other nations want to build weapons of mass destruction. The speech angers Iran and accuses Bush of interfering in Iran’s domestic affairs.

2006: Iranian President Mahmoud Ahmadinejad seeks agreement with President Bush to calm tensions over Iran’s nuclear program but defies U.N. deadlines to halt uranium enrichment. He says nuclear program is not for arms production. IAEA votes to report Iran to U.N. Security Council.

2007: U.S. announces tougher sanctions against Iran.

2008: Newly elected President Barack Obama offers to have talks with Iran over its nuclear program.

2012: U.S. imposes sanctions on Iran's central bank. Iran counters by threatening to block oil from being transported through Strait of Hormuz.

2015: Obama signs off on an agreement with the United Kingdom, France, Russia, China, Germany and the European Union in which Iran agrees to give up the means to make nuclear weapons. Iran also promises not to continue the program in secret or conduct any covert nuclear operations. In exchange, the U.S. and other world powers lift trade and economic sanctions against Iran.

May 2018: President Donald Trump declares that the U.S. will withdraw from the Iran nuclear agreement and reimpose sanctions on Tehran, a decision that angers allies who fear the prospect of a nuclear arms race in the heart of the Middle East. He says "the Iran deal is defective at its core." On state television, Iran President Hassan Rouhani says he ordered Iran’s atomic organization to start enriching uranium "more than before."

August 2018: The Trump administration reimposes economic sanctions on Iran but says he will "remain open to reaching a more comprehensive deal that addresses the full range of the regime’s malign activities, including its ballistic missile program and its support for terrorism." Rouhani, in a speech responding to the sanctions, said his country is open to negotiations but questioned Trump's sincerity.